Cerebrovascular changes in a rat model of moderate closed-head injury

We have developed and tested a rat (Wistar) model of moderate concussion. Concussion is produced by controlled and repeatable mechanical fixed, closed-head injury. Moderate concussion in this model is characterized by 4 to 10 minutes of unconsciousness, absence of skull fractures or brain contusions, and few, if any, acute neurologic symptoms. By 2 hours postinjury, the subsequent trauma is further characterized by regional and global increases in cerebrovascular permeability and decreases in cerebral blood flow. Such changes are accompanied by brain swelling and two phases of elevated intracranial pressure; one lasting about 5 hours with a peak of about 10 mmHg, the other lasting more than 3 days postinjury with a peak of about 30 mmHg. Regional neurohistologic damage detected between 3 and 4 days postinjury correlates for the most part with earlier changes in regional permeability and blood flow. Significant morphologic changes which are characterized by patchy neuronal degeneration can be found in numerous forebrain locations, particularly in the frontal (coup) and entorhinal (contre coup) cortices. These observations have important parallels in human head trauma and suggest that this reliable physiological model may be a useful, relatively simple and inexpensive tool for investigating the mechanisms and therapeutics of head trauma.